Record pressing matrix



Sept. 14, 1937. J. H. HUNTER ET AL .2,092,880

RECORD PRESSING MATRIX Filed Sept. 26, 1953 IN1/Mmes: James Ilzranfef, Guzzllil Patented Sept. 14, 1937 UNITED STATES 2,092,880 y REooRD PREssING MATRIX James H. Hunter, Lansdowne, Pa., and Julius C. Buzzelli, Beverly, N. J., assgnors to Radio Corporation of America, a corporationv of Dela- Ware Application September 26, 1933, Serial No. 691,016

5 Claims.

The present invention relates to improvements in pressing or molding means and methods such as are employed in the manufacture of phonograph records, for example, and has particular application to record pressing matrices and the method of securing the same in a conventional record press.

Heretofore, it has been customary to secure record pressing matrices in a record press by means of annular clamping rings secured in the press by means of a plurality of screws passing through the clamping rings and into the matrix supporting surfaces of the press whereby the matrices are securely helddown by the clamping rings in a manner well known in the-art.

This method of securing record pressing matrices in a conventional record press is highly objectionable for several reasons. First of all, in the pressing of a plastic record material between previously heated matrices the plastic record material spreads beyond the peripheral edge portion of the matrices and over and between the surface of the annular clamp-ing rings prior to the nal pressing movement of the press ram. Thus, when the press ram has moved o-ne of the matrices to the limit of its movement, the record material caught between the clamping rings causes unnecessary pressure to be exerted on the clamping rings themselves, particularly on the annular clamping lips formed on the inner periphery thereof.

The result of repeatedly applying such pressure on the clamping rings is to cause the matrix contacting lips on the rings to dig into the marginal edge portions of the working faces of the matrices due to the relatively soft matrix structure. Consequently, after repeated record pressing operations, the annular indentations formed in the marginal edge portion of the matrices by the clamping portion of the rings develop an annular crevice between each matrix and its clamping ring. This permits the entry of plastic material into the annular crevices, during subsequent record pressing operations, and results in the formation of a rough peripheral edge as well as an annular burr or ridge which is moulded on both sides of the record tablet at the marginal edge thereof.. v

I In order to render the records so pressed t for use, it becomes necessary to finish the peripheral edges thereof. However, the annular burrs or ridges appearing on the smooth marginal edge portions of the record tablets, after a record pressing operation, cannot be removed satisfactorily at the time the periphery of the (o1.Y 11i-5.3)

tablet is smoothed off and polished since, if v the l burrs were to be ground o-ii or otherwise suitably removed, the smooth marginal edge portions of the record tablets would become scratched and marked by similar blemishes, .thus marring and seriously detractingfrom the appearance. of the finished record tablets. l Moreover, record pressing matrices,'as utilized heretofore, have not been found to be practical into closer relation. The clamping rings were thus weakened-to the point where. they failedv to securely hold the matrices in -place- -by reason` of the yielding or breaking of the matrix engaging portions of the clamping rings.

Other disadvantages accruing as a result of the record Vpressing operation described above are the cost of replacing mutilated matrices, ex-

cessive wear and stripping of the screws utilized to secure the clamping rings in the press, and the resultant production loss due to idle presses when inneed of matrix replacements. A

Having in mind the disadvantages of conventional record pressing matrices and the manner in which .they-have heretofore beenv secured in a record press,it is an object of our invention to, provide improved record pressing matrices and clamping means therefor which are not subject to the herein noted disadvantages and objections. V

Another object of our invention is tol provide improved record pressing matrices for use in conventional record presses which do not require the use of .the customary annular clamping or retaining rings, ,Y

A further objectv of our invention is to provide improved record pressing matrices for use in conventional record presses. whereby the periphery of record tablets'or discs is completed to size and simultaneously iinished as to appearlance in the pressing thereof. n

vAnother object of our invention is to provid Vimproved record pressing matrices for use in conventional record presses whereby means separate from the matrices themselves for retard- Another object of our invention is to provide Y improved record pressing matrices for use in conventional record presses whereby record. tablets may be formed which are free from peripheral burrs, ridges and other surface irregularities.

A still further object of our invention is to' provide improved record pressing matrices for useV in conventional record presses whereby completely nished record tablets or discs may be formedV in a single pressing operation.

Another object of our invention is'to? provideYA improved record pressing matrices for use in conventional record presses which do not require the co-operation of the clamping or retaining means therefor in the complete formation of the peripheral edge of record tablets or' discs.

A further object of our invention is tof provide improved record pressing matrices and clamping or retaining means therefor in conventional record presses whereby a plastic record material is prevented from contacting'with the matrix retaining means during the record pressing operation. Y v f The foregoing objects and others ancillary thereto we prefer'to accomplishas follows:

According to a preferred embodiment of our invention, we provide record pressing matrices rwith a plurality of spaced annular ridges on the working faces thereof.V Specifically, the annular 'ridges are preferably of V formation. One annular ridge is of a diameter corresponding to the diameter of the record tablets to be pressed, the remaining annular ridges surrounding the` first -mentioned annular ridge in spaced relation thereto. Y Y l The novel features that we consider characteristie of our invention are set forth with particu- Y Vand larity in the appended claims. The invention itself, however, both as to its*v organization andits method of operation, together with additional oblaccompanying drawing in which: l

Fig. 1 is a plan View ofV our improved record Vpressing matrix in operative position on the base plate of a conventional record press,

2 is an enlarged fragmentary sectional view taken on the line 2 2 of Fig. 1, illustrating the co-operative relation of a similar matrix therewith in the formation of a record tablet,

Fig. 3 is an enlarged detail sectional view of a portion of Jone of the matrices shown in Fig. 2Q

Record pressing matrices and retaining means therefor, Vto Aovercome the defects hereinbefore enumerated, must have atleast two totally distinct characteristics; they must beY capable of withstanding repeated record pressing Voperations over considerable` periods of time without deformation of any portion of the matricesgtakng place, and they mustrbve'capable of ,producing finishedrecord tablets which areffree from all burrs, ridges or other imperfections not inherent inthe matrix structures themselves. y

Accordingly, a preferred embodiment'of our invention, referring to Figs. 1 and 2 of the drawing, is constituted by record pressing matrices of known design, each having a spiral sound groove Y ,imprinting or working surface and a plurality of raised annular ridges integral with and on each of said imprinting or working surfaces.

Specifically, three annular ridges I Il, II and I2 are formed, on veach matrix I3 and I4 concentrically with but spaced from the outermost conl volution I 5 of the spiral sound imprinting groove I6. While the three annular ridges ID, II and I2 are preferably concentric with the spiral sound imprinting groove I6, the ridges II and I2 need not necessarily be concentric therewith.

tially define the peripheral edge of the record tablet. The'annular' ridges II and I2, which are radially spaced from each other and each an- Vnular ridge I0, constitute barriers or retaining walls whereby the outward flow or spreading of the plastic record material' I1 is substantially retarded and heldvsubstantially within the bounds of the outermost ridges I2, as clearly exemplified in Fig. 2 of the drawing.

As a result ofv our improved matrix construction, the conventional annular clamping rings usually employed for retaining the-matrices I3 and I4 on thesupporting dies I9 of a record press (not shown) may be dispensed with and a plurality of suitable toe clamps 20 substituted therefor. The annular ridges I project from the working lfaces of the matrices I3 and I4 a distance Y preferably slightly less than half the thickness of a complete record tablet whereby the ridgesf n I0, during a record pressing operation and by virtue of their V configuration, co-operate and function as a circular knife edge to shear or score the pressed record material. Simultaneously with this shearing or scoringof the pressed record material by the annular ridges Il), the circumferential edge of the pressed record tablet is given a contour substantially similar to that formed heretofore on record tablets by abrading and polishing the circumferential edges thereof 55 subsequent to their formation in a record press. The excess record material beyond the circumference defined by the ridges I0 is thus substantially separated from the pressed record tablet proper to such an extent that the excess rim or flash of l" ciently above Ythe imprinting or working surfaces I6 of the matrices to substantially impede .the

outward flow or spreading of the record material II when subjected to a pressing operation.

The matrix structures I3 and I4 otherwise con,-

sist o f the conventional matrix shell 2| lwhich is suitably secured, as by soldering under pressure l sary tocircumferentially space the toe clamps 20 which retain one matrix in place with respect to the toe clamps holding the opposite matrix in place in order that the respective clamps will not come into contact with each other when the matrices I3 and I4 are brought together in a record pressing operation.

In the formation of our improved matrix, we may first cut, into the `original wax master (not shown), a series of spaced, annular grooves corresponding to the annular ridges IIJ, II and I2.

When the recorded wax master is electro-plated with a suitable metal to form a matrix shell 2|, there are left grooves 24 in the under surface of the matrix shell 2| immediately beneath each ridge I Il, II and I2, as clearly shown in Fig. 3.

Obviously, if the grooves or hollows 24 are left unsupported when the matrix shell 2| is secured to a backing plate 22, the ridges I0, II and I2 are subject to possible deformation, during a record pressing operation, by reason of the great pressure applied thereto. In order to eliminate this possibility, we preferably fill-in the grooves 24 with a suitable material, such as lead solder 25 for example, until the filled-in material is flush with the under surface of the matrix shell 2|. This prevents the normally hollow ridges I0, I I and I2 from collapsing or becoming deformed under the pressure applied thereto.

Alternatively, in the soldering or sweating of 40 the matrix shells 2| to the backing plates 22,

suicient solder may be placed between the undersurface of the shells 2| and one face of the backing plates 22 to cause sufficient solder to ow into the grooves 24 and thereby back up the in- 45 clined walls defining the annular ridges I0, II

and I2.

It is also within the scope of our invention, however, to form matrix shells which are of such size and/or thickness that backing plates therefor are 50 not required and which may, therefore, be secured directly to the heating elements of a record press.

Instead of cutting into the original wax master (not shown) a series of spaced, annular grooves 55 corresponding to the annular ridges I0, and

I2, we may dispense with the cutting of such grooves in the original wax master and form the annular ridges I0, II and I2 directly in the matrix shell 2| by pressing the said matrix shell 60 between suitable male and female die plates provided with complemental annular grooves and ridges, or we may rotate the matrix shell 2| between suitable complemental rollers, one having a circumferential ridge and the other a circumferential groove whereby the ridges I0, II and I2 may be rolled on different radii in the matrix shell 2| before it is attached to albacking plate 22.

While We have described the annular ridges I0, I I and I2 as being of V configuration, it is to be expressly understood that We may employ an- Y nular ridges having a congurationother than `that of a V.

Although we have shown and described one specific embodiment of our invention, we are fully aware that many modifications thereof are possible. Our invention,.therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

We claim as our invention:

1. A record pressing matrix of the'type adapted to form impressions in a thermo-plastic material, said matrix comprising a sound groovev pressing portion, means for forming the peripheral edge of a record tablet, and means for arresting the flow or spreading of the plastic material.

2. A record pressing matrix of the type adapted to form impressions in a thermo-plastic material, said matrix comprising a sound groove pressing surface, means surrounding said sound groove pressing surface for forming the peripheral edge of a record tablet, and means surrounding said first named means for arresting the flow or spreading of the plastic material.

3. A record pressing matrix having a spiral sound groove imprinting surface, an annular ridge of V formation spaced from and surrounding said groove imprinting surface, said ridge having a depth equal substantially to half the thickness of a record to be pressed thereby, and a plurality of similar spaced ridges surrounding said first named ridge in spaced relation thereto.

4. A record pressing matrix having a spiral sound groove imprinting surface, an annular ridge of V formation integral with the working face thereof, said ridge having a depth equal substantially to half the thickness of a record to be pressed thereby, and a plurality of similar annular spaced ridges surrounding said rst named ridge in spaced relation thereto and integraly JAMES H. HUNTER. JULIUS C. BUZZELLI. 

